Electrical circuit overload protective device



1969 u. F. CARTER 75F AL 3,478,292

ELECTRICAL CIRCUIT OVERLOAD PROTECTIVE DEVICE Filed Jan. 19. 1968 4 Sheets-Sheet l z 1' MU Nov. 11, 1969 CARTER ET AL 3,478,292

ELECTRICAL CIRCUIT OVERLOAD PROTECTIVE DEVICE Filed Jan. 19, 1968 4 Sheets-Sheet 2 I T 1. l

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3,478,292 EnfidnRIcAL CIRCUIT OVERLOAD PRQTECTIVE DEVICE.

Filed Jan. 19. 1968 Nov. 11, 1969 u. F. CARTER ET AL 4 Sheets-Sheet 4 United States Patent U.S. Cl. 337-151 7 Claims ABSTRACT OF THE DISCLOSURE A manually resettable electrical circuit overload protective device of the solder film detent typel Solder film, ratchet wheel detents for one or more circuit branches are mounted in spaced relation in an insulating housing. Pawl ended levers for each detent are mounted on a common shaft within the base and have limited lost motion rotation on the shaft. The levers normally engage their associated ratchet wheel and are individually biased to independently rotate the shaft upon release of the associated ratchet wheel in response to an overload condition. A switch operating lever mounted in the housing is biased to operate one or more switches from their normal operating conditions. A third lever secured to the common shaft moves the switch operating lever against its bias to permit the switches to return to the normal conditions when said common shaft is driven by a pawl lever, and moves an indicator plate to a position affording visual indication of overload trip operation of the device. A pushbutton reset lever whendepressed inwardly of the housing following an overload trip effects opposite rotation of the pawl lever shaft to effect reset of any released pa-wl lever on its ratchet wheel while holding the switch operating lever in tripped position.

This invention relates to an improved overload protective device for electrical branch circuit and the like.

A primary object of the invention is to provide a protective device of the aforementioned type affording positive visual indication of overload trip response. I

Another object of the invention is to provide in a protective device of the aforementioned type for increased heat transfer distances between individual branch overload responsive elements for a given basic panel mounting area to minimize the heat influence imparted between such. elements.

A still further object of the invention isto provide. in a device of the foregoing type for trip-free operation which permit reset so long as an overload condition. persists in any protective circuit branch, and

Still another object is to provide animproved manually operable reset mechanism insuring the aforementioned trip-free operation, and reset of the visual trip indication means. I 1.

Other objects andadvantages of the invention willhereinafter appear.

The accompanying drawings illustrate a preferred embodiment of the invention which will now be described, it

being understood that the embodiments disclosed are sus- 3,478,292 Patented Nor/ .1.1 9 9,

. 2 v r FIG. 5 is a view like FIG. 4, but showing the switch still another operating condition;

' FIG. 6 is a cross sectional view tak en along line 6--6 of FIG. 2; I v 1,,

FIG; 7 is a cross sectional view taken along the lipe 7 7 of FIG. 1;

. FIG. 8 is a view like FIG. 7. but showing the witch in another operating condition; FIG. 9 is a perspective view of aswitch sub-assembly used in the circuit protector switch; .Q FIG. 10 is .a top plan view of a thermally responsive detent used in the switch; and FIG. 1 1 is a cross sectional view of detent shown in FIG. 10. v 1 Referring to FIGS. 1 to .3 they show acircuit-protector switch havinga mounting plate 10, a unitary insulating housing to which plate 10 is attached, andan insulating bottom cover or base 14. The switch has a reset button 16 mounted onthe stem portion 18a of a substantially flat reset lever 18 which is reciprocally movable in a cavity 12a formed in housing 12. An electric switch unit 20, which is best shown in detail in FIG. 9, is mounted in housing 12 between the latter and base 14 which holds it in place. Switch unit 20 comprises an integral switch mounting and insulating member 20a having a substantially fiat mounting and barrier portion 20b, and substantial cubical bosses 20c and 20d formed on opposite sides of portions 20b. A normally open switch 20e has its stationary contact 20 and movable spring contactor 20g mounted on the top and bottom sides of boss 200. A normally closed switch 20h has its movable spring contactor 201' and stationary contact 20 mounted on the top and bottom sides of boss 20d. Screws 20k penetrating terminal plates 20 penetrate alined openings and clearance openings in the stationary contact and movable contacts of the switch units to secure the same in the bosses 20c and 20d.

Housing 12 is provided with a front side opening 121' into which the switch unit 20 is insertable when base 14 is removed from housing 12. As shown in FIGS. 2, 7 and 8, the forward, upper part of barrier portion 20b interfitS in a notch 12 in the base, and a lower projection 20m on portion 20b extends into a complemental recess 14a formed in base 14 to hold the switch unit in place. Three open stepped recesses 22 are formed intopof housing 12. Intermediate partition portions 13, 15, 17 and right-hand end wall 19.p rovide electrical barriers between the recesses- Combination wire terminal and overload heated mounting plates 26 are secured in place in-each of the aforedescribed recesses byscrews 24 which take into threaded recesses. One set of such plateslocated at the rear of each recess are'mounted at ahigher'levelthan theset at the front-The recess between partition portions 15 and 17 is at a higher elevation to provideincreased electrical and heat clearance from the recesses at either side thereof and also to provide clearance for themounting of switch unit 20 therebelow. 1 l H As best shown in FIGS. 10 and 11, overload detent-28 comprises an outer cylindrical insulating sleeve '32,"'-an inner cylindrical stator member 34 which extends through an opening in plate 30 and has a flange. welded to the lower surface of plate 30. Sleeve 32 is pressfittedrabout stator 34. A shaft 36 is mountedin member 34 and is restrained against axialmovement in the latter by .a C- shaped ring-37 mounted in an annular groove .36a that bears against the inner surface of the stator 349A toothed ratchet wheel or pawl 38 is non-rotatably.rivetedto'the end of shaft 36. Shaft 36 is normally held against rotation instator 34 by a solidified fill 40 of an eutectic a ley solder adhering between adjacent surfaces. As shown in the left-hand recess 22, a helic'al hea'ter sip onion coil 23. is positioned around the outer insulating "sleeve 32 of detent 28 with its ends secured by screws 25 to upper jected to the load current. Under overload current conditions the current generated in the heater coil associated withan overloaded branch will-cause the solder film to melt between shaft part 36 and the inner surface of the stator 34 and thus release shaft 36 and wheel 38 for movement as will hereinafter be more fully described.

As aforeindicated, the center recess 22 is at a higher elevation than the other two. This affords increased spacing between the heater coils 23 and thus any one of the detents will be less subject to'the heat influence of heater coils other than its own. This decreases the chances of single phasing effects, and permits decreasing the total panel mounting area of the protection device.

The ratchet wheels of the detents in the two outside recesses are engaged directly by pawls 42 which are mounted for a limited degreeof rotation on a drive shaft 44. The ratchet wheel of the detent mounted in the middle recess non-rotatably engages a coupling member 46 within a recess 46a formed in the upper end of the latter. Member 46 which is hollow throughout the major portion of its length has a ratchet wheel portion 46b formed at its lower end which is similar to and lies in a common plane with the ratchet wheels 38. Ratchet wheel portion 46b also engages a pawl 42 mounted on drive shaft 44.

The pawls 42 each comprise an integral lever portion 42a and an apertured hub portion 42b preferably formed of molded nylon. A metal ratchet wheel engaging pawl portion 420 is preferably molded in situ in lever portion 42a. The aperture 42d extending through hub 42b is semicircular with a radially inwardly extending lug 42e that is accommodated in the substantially complemental cross section of drive shaft 44. The semicircular notch 44a in shaft 44 subtends a greater angular arc than does lug 42e of pawl 42. Thus a lost motion driving connection is provided between shaft 44 and each of the pawls 42 for a purpose that will hereinafter be described.

A switch contact operating lever 48 is rotatably journaled on drive shaft 44 by means of openings formed in lever arms 48a and 48b. Lever arm 48b normally engages with the spring arm 20g of normally open contact Me of switch 20 to hold such contacts closed. Lever 48 has a third lever arm 480 that normally engages with the spring contactor 20i of normally closed contacts 20h to hold the latter open. Lever arms 48a, 48b and 480 are integrally interconnected by a portion 48d which has a spring retaining boss 48e formed therebetween arms 48a and 48b. A coiled compression spring 50 at its lower end seats around the boss 48e and at its upper end seats in a circular recessformed in the housing 12. As viewed in FIG. 7, spring 50 biases lever 48 in the counterclockwise direction in which arm 48b holds spring arm 20g closed and arm 48c holds spring arm 20i open.

As best seen in FIGS. 3 to 6, drive shaft 44 also has non-rotatably mounted therein a generally triangular shaped reset plate 52. Plate 52 has a short cylindrical boss portion 52a formed therein which is engaged by a lower edge 54a of an indicating plate 54 that is mounted in a narrow recess 12b. Reset lever 18 has a substantially L- shaped aperture 18b formed therein at the base of its stern portion 18a. A right-angle hook or tank 54b of the indicating plate extends into and can move about such aperture as 'Will hereinafter be more fully explained.

A coiled compression spring 56 which seats in a cylindrical recess 120 formed in housing 12 bears at its upper end against a forwardly extending arm 540 of the indicating plate and as hereinafter explained, tends to rotate the lat er. A. s g t y offset indicating arm 54d as will hereinafter bemore fully explained, under typical conditions extends closely toward a window 12d for-med in housing 12 which has a plastic lease or cap 12e fitted therein.

vA coiled compression spring 58 at its upper end fits about a downwardly extending tang of reset lever 18 and. bears in a short recess formed in bottom base 14. A cylindrical pin 54e is fitted in an aperture in plate 54 and extends through a generally rectangular notch 18d formed in the edge of lever 18 and into a recess 12 formed in the, inner end wall of housing 12.

.As best shown in FIG. 6,"each of the pawl arms 42a have anchored therein one end of a coiled tension spring 60 which are'each anchored at their other corresponding ends about short posts 12g extending downwardly from the triangular shaped recesses 12h formed in the bottom wall of housing 12. As viewed in FIGS. 7 and 8, springs 60 ,each tend to rotate their respective associated pawls 42 clockwise on drive shaft 44. In normal set, or untripped condition, inturned ends of the portions 420 of the pawls engage with the teeth of the ratchet wheels 38 and ratchet wheel portion 46b and are thus-restrained against rotation on shaft 44. Shaft 44, as viewed in FIG. 7, is rotationally held in engagement at its semicircular notch 44a with the lugs 42d of the pawls 42 by reset plate 52 which is held in the position shown in FIG. 3 by engagement of its boss 52a with the edge 54a of indicating plate 54. The latter plate is held in the positions shown in FIG. 3 due to the counterclockwise bias imparted thereto by spring 56.

Now let it be assumed that in use, an electrical overload condition occurs of such magnitude and duration that one of the ratchet wheel detents 28 releases to permit a ratchet wheel 38 and its shaft 36 to freely turn within a stator 34. Then the tension spring 60 will pull the pawl 42 from the position depicted in FIG. 7 to that depicted in FIG. 8. In so moving the pawl causes rotation of the shaft in the clockwise direction as viewed in FIGS. 7 and 8, and counterclockwise as viewed in FIGS. 3 "to 5. Such rotation of shaft 44 causes the edge 52b of reset plate 52 to engage lever arm 48a of contactor operating lever 48 to rotate the latter on shaft 44 to a position in which the arms 48b and 48c, respectively, disengage from spring contactors 20g and 201', respectively (see FIGS. 4 and 8).

When reset plate 52 pivots as aforedescribed, the boss portion 52a thereof bearing on the lower edge 54a of indicating plate 54 causes the latter to pivot clockise, as viewed in FIGS. 3 to 5, from the position shown in FIG. 3 to that shown in FIG. 4. In the latter position the end of the indicating arm 54d lies in close proximity to the lower surface of the lens 12e to afford visualindication from above of, the tripped condition of the overload.

device.

Resetting of the device following subsidence of an overload condition, is accomplished by manual depres sion of reset button 16 to effect increased movement of reset lever 18. As can be seen from FIGS. 4 and 5, the tang 54b of indicating plate 54 in tripped condition en: gages reset lever 18 within the short-arm of the L-shaped, aperture 18b. Thus as reset lever 18 is moved inwardly of housing 12, indicating plate 54 will be moved downwardly against the bias of spring 56 with the pin 54c moving in guide recess 12 preventing any substantial lateral movement. In so moving downwardly, the edge 54a bearing on the boss portion 52a of reset plate 52 and causes plate 52 and hence drive shaft 44 to respectivelypivot from their positions depicted in FIG. 4 to those shown in FIG. 5.

The last mentioned pivotal movement will cause any 42a will engage between adjacent teeth in ratchet wheels 8 and 4611 as shown in FIG- 7, to hold drive shaft 44 and hence retain plate 52 in the position depicted in FIG. 3.. 7

It will be noted that during the last mentioned clockwise pivotal movement of reset plate 52 and drive shaft 44, that a curved edge 54fvof. indicating plate engages with arm 48a of swtiching operating lever 48 and holds the latter against clockwise pivotal movement under the bias of spring 50. Upon reset of all pawls. 42 and release of rest button '16, indicating plate 54 moves upward under the bias of spring 56 from the position shown in FIG. 5, and also pivots counterclockwise to the position shown in FIG.- 3. During the last mentioned movement of plate 54 its edge 54 disengages from arm 48a of lever 48, and the latter is then free to pivot clockwise, as viewed FIG. 3 under the bias of spring 50 to afford reclosure of switch g and reopening of switch 201'.

It will be'noted that if an overload condition persists, or if any overload detent will not reset during the afore described resetting movements depicted in FIGS. 4 and 5, that upon subsequent release of button 16,'--drive shaft 44 and reset plate 54 will rotate counterclockwise to their positions depicteda in FIG. 4 to maintain switch 20g open and switch 20i closed. Thus the constructlon aforesdescribed affords a trip-free type of overload operation insuring that the overload responsive switches 20g and 20i cannot be reset so long as an overload condition exists.

In normal usage of the circuit protector normally open switch 20e would have its contacts connected in series with the operating coil of an electromagnetic contactor or the like. Thus, in untripped condition of the protector switch 20e would be held closed to maintain circuit to such electromagnetic contactor, and would open upon overload response of the protector to deenergize the electromagnetic contactor. Switch 20e could be connected in an electric indicating circuit to reclose upon overload response of the protector to illuminate a tell-tale lamp or other signaling device.

We claim:

1. In an electrical overload protective device, in combination:

(a) switching means having a movable element which is normally biased to one operating condition;

(b) a rotatable shaft;

(c) a lever keyed on said shaft for limited lost motion rotation thereon;

(d) means biasing said lever to effect rotation of said shaft in a given direction;

(e) an overload responsive element having means normally restraining it against movemet and egaging With said lever to hold it agaist rotation under the bias of its biasing means, said element restraining means n response to an overload condition releasing said element to permit rotation of said shaft by said lever;

(f) a switch operating lever rotatably mounted on said shaft;

(g) means normally biasing said switch operating lever rotatably on said shaft to hold the movable element of said switching means in another operating condition;

(h) a third lever nonrotatably secured to said shaft which engages with said switch operating lever to drive the latter out of engagement from said movable element when said shaft is rotated as aforestated;

(i) and reset means operable following overload response to engage with said third lever to first effect rotation of said shaft in the opposite direction to reset the first mentioned lever in engagement with said overload responsive element while holding said switch operating lever in its last recited position and thereafter upon release permitting said switch operating lever to rotate under its bias and effect the first .mentioned operation of said movable element of said switching means. v 2.. The combination according to claim 1, together with a plurality of said first mentioned levers keyed and spaced apart on said shaft, a plurality of means individually biasing said first mentioned levers to rotate said shaft, and together with a plurality of said overload responsive elements which individually engage said levers to hold them against the bias of their individual biasing means, and said levers being so keyed on said shaft that release of one overload responsive element will permit rotation of said shaft in said given direction by its associated released lever while the other levers remain engaged and restrained against movement by their respective overload responsive elements.

3. The combination according to claim 1, wherein said reset means comprises a reciprocable lever biased to an extended position and a member biased to a normal extended position, said reciprocable lever upon movement against its bias, following overload release movement of said shaft, engaging with said member to move said member in a corresponding direction wherein it effects through its engagement with said third lever rotation of said shaft in the reverse direction and engages with said switch operating lever to hold it in tripped position against the bias of its biasing means, and said reciprocable lever upon following release movement under its bias permitting said member to reciprocably move under its own bias to pivotally disengage from said switch operating lever so the latter can move to its normal position.

4. The combination according to claim 1, wherein said overload responsive element is a rotatable eutectic alloy solder restrained ratchet wheel and said lever has a pawl engageable with said ratchet wheel.

5. The combination according to claim 1, wherein said switching means comprises a normally open and a normally closed switch, each having a movable element engaged and operated to the other operating condition when said switch operating lever is rotated under its bias.

6. In an electric overload circuit protector, in combination:

(a) a housing having a bottom opening cavity, three stepped recesses formed in the upper side of said member and barriers between and electrically isolating said stepped recesses from each other;

(b) a base enclosing the bottom side of said housing;

(c) a shaft journaled for rotation in the bottom wall of said base member and held in place by said cover;

(d) at least one lever keyed on said shaft for limited lost motion rotation thereon;

(e) a spring anchored in said housing and attached to said levers and tending to cause the latter to rotate said shaft in a given direction;

(f) at least one eutectic alloy solder restrained overload element mounted in one of said stepped recesses and having a ratchet wheel portion in said housing cavity and engaging with a pawl end on an associated one of said levers to normally restrain the same from rotating said shaft in said given direction;

(g) an electric heater coil mounted in said recess in concentric arrangement about a portion of said overload element and when connected in a branch of an electrical circuit affording under given overload conditions melting of solder and rotation of said ratchet wheel to release its associated lever to effect the aforestated rotation of said shaft;

(h) a switch unit mounted in a front opening in said base and comprising at least one switch having a movable element biased to one operating condition;

(i) a switch operating lever rotatably mounted on said shaft;

(j) a spring normally biasing said switch operating lever to move said movable element of said switch to another operating condition;

(k)"a third lever nonrotatably secured to said shaft which engages with said switch operating lev'er to drive the latter out of engagement when said shaft is rotated in said given direction;

(1) and reset means mounted in another cavity in said base, and comprising an outwardly biased reciprocable -lever having a portion extending above the upper surface of said baseto which a depressable button is secured and a member biased to an upward position within the last mentioned cavity, said reciprocable lever upon movement inwardly of said base, following overloadreleaserotation of said shaft in said given direction, engaging vvith said member to move it in a corresponding direction to effect through its engagement with 'said thirdlever rotation of said shaft in the opposite direction to reset any tripped ones of said first mentioned levers in "engagement with their associated ratchet Wheels and engagement with said switch operating lever to hold it in'tripped position against the bias'of its spring,

and said reciprocablelever upon release moving under its bias to thus permit said member to reciprocably move under its bias to pivotally disengage thereof to p'rovide'increased thermal and e'lecrical isolation between the overload responsive elements mounted therein. i

. v References Cited UNITED STATES PATENTS 2,972,664 2/1961 Furnas et a]. 337-151 X 3,179,757 4/1965 Brandenberg 337-l51 X 3,223,803 12/1965 Walters 33715l X 3,258,566 6/1966 Arneberg et a1. 337-151- BERNARD A. GILHEANY, Primary Examiner B. G IL'SQN, Assistant Examiner 

